Prefabricated knockdown concrete stair construction



Nov. 7, 1961 v. HOLLAND 3,007,283

PREFABRICATED KNOCKDOWN CONCRETE STAIR CONSTRUCTION Filed April 19, 1956 2 Sheets-Sheet 1 Victor L. Hal/and INVEN TOR.

United States Patent 3,007,283 7 PREFABRICATED KNQCKDOWN CONCRETE STAIR CONSTRUCTION Victor L. Holland, R0. Box 336, Denham Springs, La.

it Filed Apr. 19, 1956, Ser. No. 579,275

2 Claims. (Cl. 50-109) Thisxinventicn relates to an improved concrete stair construction of knockdown form and wherein the es. sential componentparts; namely, the companion string.- ers, Separate pre-cast step units and foundation or footing slabs, are such in design and adaptable use that they may be expeditiously handled and transported from the source of. production to the job area and are thereafter susceptible of erection and installation at the desired doorway or other spacewith a minimum of labor, time and expenses involved.

The concept also has to do with a step and stoop combination structure characterized by and employing the aforementioned easy-toinstall components for expedient installation and erection in order that safe and comfortable access to the doorway'may be had withoutunsightly annoyance of excavations, fills, mixing materials on the job and the usual costly practices followed in the commonly utilized pouredronelocation methods.

Another object of the invention appertains to the aforementioned knockdown stair construction which involves the adoption and use ofprefabricated components or parts which will appeal to manufacturers because of simplified molding and manufacturing steps and economies and will more likely than not be endorsed by architects, contractors, home owners and other users.

Then, too, novelty is predicated on a simple, practical and compact-stair construction wherein the erection steps involving determination of the elevation, setting the footings, creating the stringers or buttresses, placing the step units and mixing and inserting the mortar are systematic and such thatthe overall construction will be endorsed by all concerned.

Stated somewhat more explicitly and structurally an important aspect of the invention has to do with a step unit comprising a tread having an endless skirt peripherally joined to the marginal edges and depending below the tread, the skirt serving to define a depending riser, a rearwardly disposed depending tongue parallel to said riser, and depending end walls at the respective transverse ends of the tread joining the respective end portions of said riser and tongue, said end walls being substantially square in-elevation and completely bridging said transverse ends and being of a height equal throughout their areas to the rise of said riserand the bottom edges thereof being coplanar with the bottom edge of said riser and being adapted to overhang, without-touching, 'the exterior surface. portions of the-respective stringers, the inward vertical surfaces of said end walls being bevelled and slanting o wardly and downwardly, the inward lengthwise s rface of said tongue being likewise bevelled and slanting rearwardly and downwardly, said tongue being of a cross-sectional dimension appreciably less than the cro -sec ionaldim nsions of said riser and end walls and, having a fiat bottom edge disposed in a plane spaced vertically above the aforementioned coplanar bottom edg s o said riserand end walls, and transverse ribs f rmed on he underneath surfaceof said tread and being spaced fr m the inwar ertical surfaces of their respec live and walls and parallel thereto and having their for-v ward sndsvintes ated wit he rearward surfaces of the pp portions of said ris r and th ir rearward ends joined to the bevelled lengthwise inward surfa es of said tongue, said ribs havinssubstantial y the same crosseectional dimension as. said tongue and having flat bottom edges co planar with the companion bottom edge of said tongue, the outwardly disposed vertical surface of each rib slanting downwardly, inwardly and away from the complemental slanting surface of the adjacent end wall, each rib, end wall, and the respective bridging portions of the riser and tongue defining and providing a relatively deep stringer keying and mortar receiving pocket.

Although it is common in the trade to notch and otherwise construct the upper edges of so-called stringers to provide vertical riser abutments and tread seating surfaces and to otherwise provide a so-called stepped edge, the instant invention features an improvement wherein each tread supporting or receiving surface is notched at its point ofjuncture with the riser abutment, the notch being quite long and reaching forwardly and having its forward edge bevelled. This provides for an improvement wherein the step unit which has a locking tongue which seats in the notch or groove is such in cross-section that approximately one-half portion of the groove projects beyond the tongue to provide clearance space and to facilitate repairing a given step unit by replacing the same in a manner to be described.

Other objects, features and advantages will become more readily apparent from the following description and the accompanying sheets of drawings.

in the drawings, wherein like numerals are employed to designate like parts throughout the views:

FIGURE 1 is a perspective view of a stair construction constructed in accordance wtih the principles of the present invention and showing the manner in which the same is set up or erected for use; 7

FIGURE 2 is a view taken on the irregular vertical line 2-12 of FIGURE 1, looking in the direction of the arrows, and showing portions in section and also in elevation and with the stringer facing the observer broken away at the left to expose the inside of the stringer on the other side and away from the observer, said view also showing approximately how a step unit may, in case of damage, be replaced;

FIGURE 3 is a perspective view of one of the step units with the right hand end portion broken away to I show the underneath pocket construction;

FIGURE 4 is an exaggerated perspective view showing one end of one of the step units in section and one of the cooperating portions of the stepped edge of the stringer and its construction;

FIGURE 5 is a section on the line 55 of FIGURE 1 looking in the direction of the arrows; and

FIGURE 6 is a fragmentary section through one end portion taken on the vertical line 6-6 and looking in the opposite direction.

The prefabricated ,or precast concrete wall members may be here described as either butresses or, by preference, stringers. One stringer is shown and denoted by the numeral 8 in FIG. 2 and the other one by the numeral 10. Actually, however, these stringers are identical in construction. However, in FIG. 2 it is to be pointed out that the outside wall of the stringer 8 is denoted at 12 and the inside wall of the stringer 10 at 14. So looking at FIG. 2 one sees the left hand end of the stringer 8 terminating to the right of the corresponding end of the Stringer 10. The stringers in practice are set up or positioned on appropriate foundation slabs or blocks 16 which are of no particular concern in this ap plication. The stepped upper edges of the stringers are identical and. each stepped edge portion is made up of step unit features. As shown, for example, in FIGURE 4 each step portion is characterized by a vertical abutment 18 and a horizontal tread supporting surface 20. At the angular junction of these two surfaces 18 and 20 the surface 20 is recessed to provide a keeper notch or groove 22 which,

it will be noted has its side portions opening through the respective inner and outer sides of the body of the stringer and said groove being appreciably long and having its forward or leading edge bevelled upwardly as at 24. In casting or prefabricating the stringers suitable reinforcing wires, rods or the like as denoted at 26 in FIG. 2 are employed.

Although the invention contemplates the use of a stoop under certain circumstances it is not herein shown and only the step units are revealed. Each precast concrete step unit is the same in construction and, obviously a de scription of one will suflice for all. To this end each step unit is denoted by the numeral 28.

The step unit comprises a flat-faced substantially rectangular tread 30 having an endless skirt peripherally joined to and depending from the four marginal edge portions of the tread. Thus, the skirt and tread constitute an inverted pan-like unit which lends itself to expedient production in a mold shown, for example, in Patent No. 2,713,710 of July 26, 1955 which has been granted to me. Actually the skirt, so-called, is made up of four depending walls. The forwardly disposed vertical wall, however, defines a rectangular riser 32 which is of a length commensurate with the length of the tread and of appropriate rise. Extending rearwardly from the opposite or respective end portions of the riser are vertical end walls 34 and it will be noticed in this connection that each end wall, sometimes called a skirt portion, has the same rise as the riser. In end elevation it is square and it reaches from the forward to the rearward edge of the tread. This large areal extent of the wall 34 is important and it is also important that the bottom flat' edge 36 thereof terminate coplanar with the flat lower edge 38 of the riser 32. It will be evident too that these end walls are tapered in cross-section so that the surfaces slant downwardly. I am particularly concerned with having the interior surface bevelled so that it will slant downwardly and outwardly as at 39. In this surface there is a keying groove 40 for mortar. Reverting to the skirt it also embodies a rearward shorter wall which provides a reinforcing and keying tongue and this is denoted by the numeral 42 and it will be seen that its lower fiat edge 44 terminates in a plane above the plane of the coplanar edges 36 and 38. The end portions of this wall or tongue 42 join with the upper end portions of the end walls or skirt portions 34, all as brought out in FIG. 3. It will be further noticed that the leading or forward lengthwise surface of the tongue 42 is beveled downwardly and outwardly as at 46. Formed integral with the underneath surface 48 of the riser are transverse ribs 50. These join at their forward and rearward ends to the cooperating surfaces of the riser and tongue respectively. Each rib is spaced inwardly from the beveled interior surface 39 of the end wall 34. The cross-section of the rib is equal to that of the tongue. Therefore the lower edges of the ribs are coplanar with the lower edge 4 of the tongue. The end portions of the tongue therefore interconnect the end portions of the end wall 34 and the rib 50 and the same is true at the front where the riser bridges and connects the forward end of the rib and the forward end of the end wall. These several components; namely, the end wall 34, rib 50 and cooperating bridging-portions of the riser 32 and tongue 42 provide a substantially rectangular keying and mortar receiving pocket. Particularly is it to be noted that the pocket is thus walled in and closed around its margins. It is therefore not an open ended channel in any sense of the word. It is further noted that the length of the grooves or notches 22 is appreciably greater than the crosssection of the tongue 42 whereby the forward half portion of each groove extends beyond the beveled surface 46 of the tongue to provide the clearance space usable in the manner shown in FIG. 2.

Reverting to FIG. 2 this view shows the stair construction erected and ready for use except where one of the centralstep units is shown cocked or at an angle. The

purpose of this illustration is to show that by properly lengthening the grooves 22 ad beveling the end portions 24, sufiicient clearance is bad so that it is possible to handily replace a damaged or broken step if and when necessary. Some contractors require this type of construction and in practice all that it is necessary is to crack or break the damaged step and to dislodge it and to then replace it with a new step unit in what is believed to be an approximately obvious manner from the illus tration depicted in FIG. 2.

Reverting to the ribs 50 it will be seen that the outer vertical faces slant inwardly and downwardly as at 52 and there is an additional mortar keying groove or channel 54 provided in the slanting surface 52. FIGS. 5 and 6 are utilized here to bring out the fact that the crosssection of the stringer 8 is less than the width of the keying pocket into which the tread seating surface 20 telescopically extends. It follows, therefore, when the mortar is placed atop the seating surface as shown at 56, for example, spaces are provided on opposite sides thereof, there being a V-shaped pocket-like space between the end walls 34 and the exterior surface of the stringer 8 and also a similar space between the surface 52 of the rib 50 and the interior vertical surface of the stringer. These spaced parallel V-shaped or wedge-like pockets facilitate not only the use of wooden wedges (not shown) and the like in erecting and installing the step units, but

- provide pockets-into which the mortar pack may be readily and conveniently chucked or troweled into place.

It is significant to note that the step units are also reinforced with suitably embedded reinforcing elements. Particular attention is directed to the fact that the reinforcing elements 58 in the skirt portions or end walls 34 1 provided between the pockets at the ends of the step units and the tread seating surfacesof the stringers which project into the pockets, it is to be noted that each tread is positioned on the buttress or stringer and is pressed firmly in place. That is to say, the mortar is pressed firmly into the pockets and stays put. This can be accomplished most thoroughly with the finger tips. Care must be exercised to see that all mortaring is done thoroughly in order to ensure stability of the finished job. Concerning the step of mortaring the overhanging walls, that is, the pockets between the surfaces 38 and 12, by using a flat piece of plywood, Masonite or shingle (not shown) one is permitted to press the outside pockets full of mortar and pack the same until they will take no more mortar. Then the excess mortar is cut off with a small pointed trowel. Then, too, in practice it is desirable to mortar the cross seams 60 as evident (FIGS. 2 and 6) using wet mortar to a slightly more plastic state and to utilize a small pointing trowel and depress the mortar firmly into the cross seams. This is not too important insofar as the structure is concerned.

The construction is such that the builder is able to quickly complete the step work under any weather conditions allowing immediate use of the steps and completely eliminating the need for barricades. I

This application is a continuation-in-part of my copending application Serial No. 91,808, filed on May 6, 1949 and now abandoned.

Reverting to the wedge-shaped cross-section of the ribs 50 and the depending walls of the peripheral skirt it will be obvious that the construction adopted and shown is advantageous in that it expedites the molding and casting of the unit, as an entity, in a simplified pan-type mold covered in my previous Patent 2,713,710.

Touching again on the depth of the reinforced walls 34 it will be observed that they rely on this additional area to minimize lateral splitting found commonly in other precast step tread constructions, Then, too, these walls 34 expedite stacking for storage, transportation and handling, a feature not present in analogous prior art adaptations.

Also, with further reference to the loose joint seen in FIG. Sat the left wherein the cross-section of the stringer is appreciably less than the width of the pocket, this play not only provides the additional space and pockets for advantageous application and retention of the mortar packs ensuring stability, it is a highly desirable construction in that it obviates resorting to periodical but impractical close tolerances supposedly existing in interlocking tongue and groove constructions in prior art adaptations.

What is claimed as new is as follows:

1. A prefabricated stair construction comprising, in combination, a pair of precast duplicate stringers each having stepped upper edgesembodying a plurality of stepped portions, each step portion embodyinga vertical riser contacting and stabilizing abutment, a right angularly disposed forwardly extending tread seating surface and an elongated keeper groove recessed in said seating surface at the angular junction thereof with the lower portion of said abutment, the forward end of said groove being vertically bevelled, said pair of stringers being vertically supported in spaced parallelism and the abutments and seating surfaces of one stringer being situated opposite to the respective abut-ments and seating surfaces of the other stringer, a first step unit comprising a horizontal tread generally rectangular in plan and having an endless skirt peripherally joined to and depending from its four marginal edge portions, said skirt embodying a forwardly disposed vertical wall providing a riser commensurate in length with the front lengthwise edge of the tread, a pair of vertical rearwardly extending end walls connected with the respective end portions of said riser and providing skirt portions equal in rearward reach to the transverse width of said tread, said skirt portions having a rise equal to the rise of said riser and having their bottom edges coplanar with the bottom edges of said riser, the underneath surfaces of the end portions of said tread inwardly of said skirt portions resting atop their respective seating-surfaces and said skirt portions overhanging and having their entire inward vertical surfaces spaced outwardly from the outer vertical surfaces of said stringers, said skirt also embodying a lengthwise rearward wall providing a reinforcing and keying tongue parallel to said riser and joined at its respective ends to adjacent end portions of said skirt portions, said tongue being commensurate in length with said riser and having its lower edge disposed in a plane spaced vertically above the plane of the aforementioned coplanar bottom edges of the riser and skirt portions, the respective end portions of said tongue being seated in and Wholly bridging their respective keeper grooves and extending through and beyond both open side portions of their respective grooves, transverse ribs formed on the underneath surface of said tread and disposed in spaced parallelism relative to the inner upper portions of the vertical surfaces of said skirt portions and having their forward ends joined to the rearward interior surfaces of said riser and their rearward ends joined to the forward interior surfaces of said tongue and the bottom edges of the ribs being flush with the bottom edge of said tongue and, in conjunction with said tongue, riser and skirt portions, defining relatively deep pockets, the latter being closed front, back, and sides, the adjacent tread seating portions of said stringers being telescopically confined and centered in their respective pockets and being of a thickness less than the width of the pockets, and bonding material filling the respective pockets and also lodged in the pocket-like spaces between the outer surfaces of the stringers and inner surfaces of said skirt portions, a second step unit identical in construction with said first step unit and likewise supported on the stringers, the rear edge of the tread of the second step unit underlying the bottom edge of the user of the first step unit, said grooves each being of a length appreciably greater than the cross-sectional dimension of said last-named riser and cross-sectional dimension of the portions of the tongue which are seated in said grooves, so that the forward bevel-ended half-portions of the grooves underlying the tread of said second step unit extend well beyond the front surface of the riser of the first unitand also well beyond the tongue which is seated-in said grooves whereby to afford available clearance spaces in front of said tongue for step replacement purposes.

2. A prefabricated stair construction comprising, in combination, a pair of duplicate precast stringers, each stringer having stepped upper edges, each stepped portion of each upper edge embodying a vertical riser-contacting abutment, a forwardly extending horizontal tread-seatingsurface, and an elongated keeper groove recessed in said seating-surface at the place of juncture thereof with said abutment, the respective inward and outward sides of said groove opening through the inner and outer vertical surfaces of the stringer, said pair of stringers being vertically supported in spaced apart parallelism and the abutment and seating surface of one stringer being situated opposite to the respective abutment and seating surface of the other stringer in cooperating step building relationship, and at least one precast step unit comprising a horizontal tread generally rectangular in plan and having a deep endless skirt peripherally joined to and depending from its four marginal edge portions, said skirt embodying a forwardly disposed vertical wall providing a riser commensurate in length with the front lengthwise edge of the tread, a pair of vertical rearwardly extending end walls connected with the respective end portions of said riser and providing skirt portions equal in rearward reach to the transverse width of said tread, said skirt portions having a rise equal to the rise of said riser and having their bottom edges coplanar with the bottom edges of said riser, the underneath surfaces of the end portions of said tread inwardly of said skirt portions resting atop their respective seating-surfaces and said skint portions overhanging and having their entire inward vertical surfaces spaced outwardly from the outer vertical surfaces of said stringers, said skirt also embodying a lengthwise rearward w-all providing a reinforcing and keying tongue parallel to said riser and joined at its respective ends to adjacent end portions of said skint portions, said tongue being commensurate in length with said riser and having its lower edge disposed in a plane spaced vertically above the plane of the aforementioned coplanar bottom edges of the riser and skirt portions, the respective end portions of said tongue being seated in and wholly bridging their respective keeper grooves and extending through and beyond both open side portions of their respective grooves, transverse ribs formed on the underneath surface of said tread depending below said underneath surface and disposed in spaced parallelism relative to the inner upper portions of the vertical surfaces of said skint portions and having their forward ends joined to the rearward interior surfaces of said riser and their rearward ends joined to the forward interior surfaces of said tongue and the bottom edges of the ribs being flush with the bottom edge of said tongue and, in conjunction with said tongue, riser and skirt portions, defining relatively deep open bottom pockets, the latter being closed front, back, and sides, the adjacent tread seating portions of said stringers being telescopically confined and centered in their respective pockets and being. of a thickness materially less than the width of the pockets to obviate requirements for close tolerances and to provide clearance on opposite sides thereof permitting the step unit to be properly positioned regardless of any irregularities or warpage of the stringers, and bonding material filling the respective pockets and also the deep pocket-like spaces between the outer surfaces of the stringers and inner surfaces of said skirt portions, each groove of a length appreciably greater than the cross-sectional area of said tongue so that the forward half-por- 7 tions of the grooves extend well beyond the forward ver- 2,441,617 tical wall of said tongue and being vertically bevelled, 2,515,823 whereby to facilitate, whenever necessary or desired, replacing said step unit.

5 13,067 References Cited 1n the file of this patent 137,466

UNITED STATES PATENTS 2,232,905 Dyer Feb. 25; 1941 8 Clark May 18, 1948 Dettling July 18, 1950 FOREIGN PATENTS Denmark Mar. 21, 1910 Austria May 11, 1934 

